Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $41.33   12.786%   $46.6145   $46.61   $46.60   $46.60  
  Purchase #2 $36.38   12.114%   $40.7871   $40.79   $40.80   $40.80  
  Purchase #3 $160.85   7.317%   $172.6194   $172.62   $172.60   $172.60  
  Purchase #4 $134.86   6.874%   $144.1303   $144.13   $144.15   $144.10  
  Purchase #5 $200.42   9.402%   $219.2635   $219.26   $219.25   $219.30  
  Purchase #6 $67.58   10.161%   $74.4468   $74.45   $74.45   $74.40  
  Purchase #7 $248.28   8.399%   $269.133   $269.13   $269.15   $269.10  
  7 purchase totals = $889.70       $966.9946   $966.99   $967.00   $966.90